Occurrence, removal and risk evaluation of ibuprofen and acetaminophen in municipal wastewater treatment plants: A critical review

Ibuprofen and acetaminophen as two anti-fever agents have been widely used in human. Due to lack of full understanding, this work firstly summarized their occurrence and fate in municipal wastewater treatment plants (WWTPs) across 30 countries. The respective influent concentrations of ibuprofen and acetaminophen were not detected (ND)-39,830,000 and ND-66440000 ng/L, while their corresponding respective effluent concentrations were ND-58710 and ND-90500 ng/L. The removal efficiencies of ibuprofen and acetaminophen in municipal WWTPs were 6.5-100 % and 14.3-100 % with respective average removal efficiencies of 87.6 % and 94.7 %. There have been many batch studies on ibuprofen biodegradation with kbio values available, while such investigation for acetaminophen was very limited. The theoretically calculated removal efficiency of ibuprofen with kbio agreed well with that of the observed average removal efficiency of on-site investigations on full-scale WWTP, which was quite different from natural estrogens and some other emerging contaminants. One possible reason is that conjugated ibuprofen could be easily cleaved and the cleavage step gives little effect on the biodegradation of ibuprofen. Due to extremely high concentrations of ibuprofen and acetaminophen in influent of municipal WWTP, their concentration levels in effluent likely high enough to pose adverse effects on some aquatic organisms. To protect water environment, advanced treatment is necessary to further remove residue ibuprofen and acetaminophen in the effluent. To the best of our knowledge, this is the systematical summarization on the occurrence and fate of ibuprofen and acetaminophen in municipal WWTP as well as their potential effect on aquatic organisms, which addressed known knowledge and unknowns to be further investigated.